Watercraft which are designed to operate in the planing mode are well known. Empirical evidence based on naval architecture and hydro-dynamic research, testing and experimentation has established beneficial performance attributes from three important features of such watercraft.
First, flat bottom planing hull surfaces with 0 degree deadrise angles are known to achieve the most efficient planing lift forces when operating at optimal trim angles. A watercraft utilizing flat planing surfaces will therefore generate more efficient planing lift than one with planing surfaces with higher deadrise. However, conventional wisdom is that a watercraft with exclusively flat planing surfaces cannot achieve high seakeeping and seakindliness in rough seas.
Watercraft with a relatively flat or shallow V planing hull bottom, as measured relative to the horizontal, have efficient planing lift and are very stable, but have very poor seakeeping in rough seas, i.e., they also lack seakindliness and directional stability in rough seas.
Consequently, watercraft with a deep V hull bottom were developed to introduce better seakeeping and directional stability. The hulls of such boats, as taught in U.S. Pat. No. 3,237,581 and U.S. Pat. No. 3,085,535, are typically “V” shaped in cross section, with each leg of the V being generally flat and forming an angle to the horizontal, known as the deadrise angle, of approximately 20 to 30 degrees. The deadrise increases toward the forward end of the boat, and as a general rule, has a deadrise greater than 43 degrees at the bow to provide a fine entry. As such boats move forward in the water the narrow bow entry slices through the water, while the flatter surfaces aft provide some planing area, providing a balance between planing lift and seakeeping.
The planing lift for conventional deep-V hulls is typically augmented by the provision of running strakes on the hull surfaces as shown in FIG. 1. These strakes are usually strips of triangularly shaped elements, in cross-section, appended to the outer hull surface that provide additional surface area for additional lift. They also cleanly separate water flow off the hull to reduce spray and drag. Indeed these strakes were originally called “spray strips.”
Despite the improvements found with the deep V hull design, planing boats can provide uncomfortable rides. With too high a running trim, the bow pitches up over the crest of the wave, then plunges downward slamming back to the free surface. Another type of slamming occurs when the hull completely leaves the water, and is called re-entry slamming.
Conventional deep-V hulls will have excellent seakeeping if they can be controlled to run at speed with low trim while remaining upright (i.e., not heeled to either side). The stable mode of operation with the waterflow along the hull is shown in FIG. 2a. Maintaining a conventional planing hull upright however is difficult to achieve since the deep-V hull is characteristically soft in roll and will heel in response to any asymmetric load such as weight shift, propeller torque, cross wind and waves. A dynamic system may be added to control the boat attitude; however, this adds complexity and cost.
When a deep-V boat heels to either side, its effective deadrise is decreased by the heel angle such that it loses the low slamming benefits of a deep-V hull. For example, a 24 degree deadrise hull heeled over by 10 degrees becomes a 14 degree deadrise hull normal to the water surface. In very high seas, it is not atypical for a small craft to experience up to 15 degrees of heeling so that the effective 9 degree deadrise surface is relatively flat to the water and pounds in waves, as illustrated in FIG. 2b. 
A particularly dangerous condition in which to have excessive roll is when turning in rough seas from a head to a quartering to a beam sea. Heeling over during this maneuver causes excessive pounding and uncomfortable to dangerous levels of roll.
A steeper deadrise than conventional deep V hulls would greatly improve the seakeeping and seakindliness of the hull. Even when heeled over, the surface of a deeper V hull will retain a significant deadrise relative to the water surface and thus cushion any impacts. Furthermore, the higher deadrise hull has less pitch excitation, thus allowing the hull forebody to penetrate the wave rather than kiting off of it. One such example is shown in U.S. Pat. No. 3,415,213. However, it appears that several problems must be resolved before a planing monohull with an extremely high deadrise can be successfully reduced to practice. For example, an extremely deep V hull has greater stability problems than a deep V being even more tender in roll. Further, although the orientation of its surfaces relative to the water improves its seakeeping and seakindliness, an extremely deep V hull also produces far less dynamic lift than a flatter hull. The inadequate planing lift of a deeper V makes getting over critical speed, also called hump speed, more difficult, reduces the payload capacity, and increases operating draft. In addition, the limited hull width of an extremely deep V restricts arrangements and has low internal volume.
Also, narrow watercraft hulls with ultra high deadrise angles greater than 50 degrees and typically greater than 60 degrees in forward sections are known to transit through waves by penetrating and slicing into them with less heave and pitch vertical motion excitation than a hull with lesser deadrise, thereby improving a watercraft's seakeeping and seakindliness. The hull can have sufficient vertically arranged and increasing buoyant volume to provide progressive lift to counter hull plunging motions when transiting through wave troughs; however, conventional wisdom on these vessels is that a watercraft with ultra high deadrise panels cannot achieve high lift and planing efficiencies.
Finally, monohulls, with higher fineness ratios, improve seakeeping of watercraft but can have static and dynamic stability issues as well as non-optimal running trims. However, conventional wisdom is that a narrow planing hull is not as efficient as a wider hull and cannot carry as heavy loads. But, watercraft with entrapment tunnels and amas improve a narrow vessel's stability at rest or at speed and improve the vessel's ability to achieve critical planing speeds and carry high loads.